Recently, it has become a practice to install a starter motor on the engine of reasonably light portable equipment such as a chain saw, a weed cutting machine and the like, to avoid the pull-start recoil starting operation commonly used. The internal combustion engine for a portable equipment for which a small high output is required is generally of a two-cycle type provided with a diaphragm type carburetor capable of coping with a variation in an attitude of a machine body, in which when the engine is started, a proper mixture can be supplied in accordance with the operating conditions and temperature conditions.
For example, Japanese Patent Application Laid-Open No. 35047/1987 discloses an arrangement wherein when the engine is started, a fuel is supplied by a manual primer pump from a fuel tank to a metering chamber of a carburetor and at the same time a fuel is also filled into an accumulator, and simultaneously with the recoil operation of the engine, the fuel in the accumulator is supplied by the operation of a button from a fuel nozzle to an air intake passage of the carburetor to produce a rich mixture necessary for the start.
In the case of the engine provided with a starter motor, such a manual operation is cumbersome, and if the motor is driven uselessly, a source battery becomes consumed.
In view of the foregoing, an object of the present invention is to provide a start-fuel supply in an internal combustion engine for a portable equipment in which a start-fuel pump is driven by a starter motor to inject a predetermined quantity of start-fuel to an air intake passage to thereby produce a rich mixture necessary for the starting of the engine.